The present invention relates to a novel vessel scraper. The inner walls of vessels require cleaning for a variety of reasons. Often it is desired to maintain the vessel in a closed condition when such cleaning is necessary. Certain chemical operations utilize continuous scraping, for example, fractional crystallization.
Typical of such a process is the necessity of rapid and efficient heat exchange to freeze-out a particular solute from a solution. Crystallization on the inner surface of the crystallizer interferes with the cooling mechanism effecting such crystallization. Consequently, mechanical stirrers or scrapers have been employed on small scale crystallizers in the form of helical ribbons or spiral blades to keep the crystallization surface clean.
Large crystallizer vessels of cylindrical form are generally fabricated by welding plates together. The resultant vessel possesses an out-of-roundness and/or "banana" shape because of the nature of the fabrication. Accurate machining of large cylindrical vessels lends itself to the out-of-roundness problem, but this procedure is prohibitively expensive to accomplish. Prior scraper mechanisms have been rigidly constructed which has resulted in loss of efficiency requiring costly interruption of the crystallization process, for failure to accommodate construction imperfections or uneven build-up of crystallized materials.